Electronic devices such as computers, media players, and cellular telephones typically contain audio jacks. Accessories such as headsets have mating plugs. A user who desires to use a headset with an electronic device may connect the headset to the electronic device by inserting the headset plug into the mating audio jack on the electronic device. Miniature size (3.5 mm) phone jacks and plugs are commonly used electronic devices such as notebook computers and media players, because audio connectors such as these are relatively compact.
Headsets and other accessories have speakers that can be used to play back audio for a user. Some accessories have microphones. Microphones can be used to pick up the sound of a user's voice. This allows an electronic device to be used to record voice memos. Electronic devices with cellular telephone circuitry can use a microphone on an accessory to gather the user's voice during a telephone call.
In some headsets, microphones are used to form part of a noise cancellation circuit. When noise cancellation functions are active, the impact of ambient noise on audio playback can be reduced. Microphones can also be used to implement voice microphone noise cancellation.
Noise cancellation operations are generally implemented using analog noise cancellation circuitry. The analog noise cancellation circuitry subtracts a weighted version of the microphone signal from the audio signal.
Although conventional noise cancellation circuit arrangements can be satisfactory in some situations, recent advances in headphone quality and audio playback fidelity are placing increasing burdens on conventional noise cancellation circuits. These burdens are making it difficult or impossible to implement desired levels of noise cancellation performance with conventional approaches.